A bracketed group did not take the power that followed it. The branches
for `(`, `[` and `{` returned from the reader before the call that
attaches superscripts and subscripts, so `(a + b)^2` was set with the
caret as an ordinary symbol and the 2 beside it, and
`\left( x \right)^{2/3}` came out as `(x)^2/3` with the caret visible.
Inside a fraction it was worse: `\frac{1}{\left(1 - e^2\right)^{3/2}}`
put the `3/2` after the fraction, so the exponent hung outside it. A
bracketed group is a base like any other and is now given its scripts by
the same call as everything else.
Two more of the same kind were found while fixing it. A style command
such as `\mathbf` dropped the subscript of `\mathbf{a}_{...}`, and the
vertical bars were not known at all: `\lvert` and `\rvert` were shown as
the letters of their own names, which also lost the power after them.
The check on the formulas compared the characters and so missed all of
this, because every character was present and in the wrong place. It now
also asserts what the notation means: a caret and an underscore say what
to raise or lower and are never drawn, so one that reaches the output is
a script that was never attached. That single assertion found the two
further cases on its first run.
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